Are Road Accidents Affected by Rainfall? A Case Study from a Large Indian Metropolitan City

The projected 40% increase in global deaths resulting from injury between 2002 and 2030 is predominantly due to the increasing number of deaths from road traffic accidents. Road crashes deserve to be a strategic issue for any country’s public health and can lead to overall growth crisis, if not addressed properly. World Health Organization (WHO) warned that alarming situation is coming in future days as some studies predicted that without appropriate action, by 2020, road traffic injuries will be the third leading contributor to the global burden of disease in terms of DALYs (‘disability-adjusted life years' i.e. Years of life lost to premature death and also years lived with a disability, adjusted for the severity of the disability). India already accounts for about 9.5% of the total 1.2 million fatal accidents in the world. In 2007, 1.14 lakh people in India lost their lives in road mishaps — that’s significantly higher than the 2006 road death figures in China, 89,455. One person dies at every 4.61 minutes in India for road crashes. Road deaths in India registered a sharp 6.1% rise between 2006 and 2007. Road crashes are complex interaction of different parameters like road, vehicle, environment, human etc. Skidding of road vehicles is considered as one of the major causes of road accidents occurring all over the world. Skidding, caused by lack of tire-to-road friction, is one of the most important single causes of traffic accidents. This paper aims to critically analyze the weather and wet road related crashes. Critical analysis of wet road driving conditions due to rainfall and 1966 number of road crashes from a large Indian metropolitan city has also been presented in this paper. It has been found that nearly 19% of total crash took place in wet days. It has been noted that the value of rain-crash-effect were positive for seven months for year 2006 and none of them had the highest rainfall. A negative rain-crash-effect during months with high rainfall may be the results of small dry spell, extra care of drivers during rainy days, low vehicle speed due to traffic congestion and runoff effect. High values of rain-crash-effect during March, April, August, October and December months may be explained by dry spell effect. It is clear that dry spell has positive and significant effect over average rain-crash-index. Shift from ‘no dry spell’ to ‘small dry spell’ (1-5 dry days) increased the average rain-crash-index by 23.3% and shift from ‘small’ to ‘large dry spell’ (>5 dry days) increased the average rain-crash-index by 115.7%. An enhancement of the accident count and average rain-crash-index after a dry spell could be due to physical or psychological factors, e.g., the build-up of oil and dirt on the road surface or the slow mental realignment to wet conditions. Trend of the relationship of rainfall class and ‘rain-class-crash-rate’ revealed that heavy rainfall reduced ‘rain-class-crash-rate’ than drizzling or light rainfall. Different probable physical and psychological reasons are discussed to analyze the rainfall class effect. In general, rainfall creates driving hazard. But rainfall hazard is complexly related with road crash and needs more specific and distinguished research rather than general approach to minimize rainfall related road crashes.